Some vehicles, and particularly trucks, employ a front engine power takeoff (FEPTO) to drive accessory components such as generators, snowplows, hydraulic lifts, cement mixers, hoists, drills, etc. Such FEPTO assemblies are usually coupled to the front end of the vehicle engine in a position which interferes with, or competes for space with, the vehicle radiator, and if the vehicle has one, the charge air cooler used to cool turbo-charged engine intake air. The conventional approach to this problem is to construct the radiator core with a notch or opening which receives the front engine power takeoff.
Radiator 10 is generally formed in a conventional manner and includes an upper manifold 13 and a lower manifold 14 each connected to core heat exchange tubes, usually finned, for the flow of a coolant, such as water or water and glycol, through core 11. Although the direction can be reversed, as shown in FIG. 1, coolant from the engine block enters manifold 13 at inlet 16 and exits outlet manifold 14 to return to the engine at outlet 17.
In order to accommodate the through-the-radiator FEPTO a midway manifold 18 is provided which is coupled by conduit 19 to outlet manifold 14. Thus, coolant entering tubes in a middle portion 21 of radiator 10 from inlet manifold 13 flows downwardly to midway manifold 18 and from the midway manifold down conduits 19 to outlet manifold 14 and back to the engine.
The use of a midway manifold to provide the necessary hole or opening in a heat exchanger having liquid-based coolant, is practical, but it does increase the cost of construction of the heat exchanger or radiator. The use of such a heat exchanger structure for heat exchangers employing a gas as the working fluid, such as charge air coolers, however, is not desirable.
Charge air coolers are heat exchangers in which the working fluid is air, namely, engine intake air which has been heated as a result of compression by a turbocharger. Many trucks employ a heat exchanger, charge air cooler, between the outlet of a turbocharger and the air intake of the engine in order to dissipate some of the heat generated during turbocharging or compressing of the air.
Such charge air coolers require substantial surface area to produce the desired temperature drop, and they must be operated on elevated pressure to maintain the benefits of turbocharging. Charge air coolers are usually mounted in front of a conventional water-based radiator, which means that the same problem of competition for frontal space between a charge air cooler and a FEPTO occurs.
Three general approaches in the provision of charge air coolers in vehicles having FEPTOS have been employed to accommodate the FEPTO. First, the charge air cooler can be mounted in cooling air in series in front or behind the radiator and have a construction as shown in FIG. 1. Second, the charge air cooler can be mounted in series with the radiator, but with the charge air cooler not extending below the midway manifold. Third, the charge air cooler can be mounted in parallel above or below the radiator, instead of in front of it. The last approach often is not practical because of limited front end space in many vehicles. The second approach can reduce the core volume, and particularly the length of the heat exchange tubes, sufficiently to prevent the necessary heat transfer to produce the desired intake air cooling.
The use of a heat exchanger having a structure as shown in FIG. 1 for a charge air cooler has several disadvantages. First, as is true for water-based radiators, a midway manifold and notched core inherently adds to the cost of the radiator. Moreover and more importantly, air under pressure is more difficult to contain than water. Under the thermal stresses which result from core tubes of different lengths and a midway manifold, the cost of manufacturing a reliable and durable charge air cooler having a FEPTO opening increases very dramatically. In practice such charge air coolers have not been found to reproducibly achieve the desired durability.
Accordingly, it is an object of the present invention to provide a durable and yet economical charge air cooler which can be mounted directly in front of the radiator assembly of a truck or the like and accommodate a front engine power takeoff.
It is another object of the present invention to provide a heat exchanger assembly for a vehicle, such as a truck, through which a front engine power takeoff drive mechanism can be routed.
It is still another object of the present invention to provide a charge air cooler which is constructed in a manner accommodating both a front engine power takeoff and another heat exchanger device mounted to receive cooling air in parallel to said charge air cooler.
Still a further object of the present invention is to provide a charge air cooler which is economical to construct, can be retrofit to a variety of vehicles, is adaptable to a variety of front engine power takeoff mechanisms, and minimizes thermal stresses.
The attainment of the foregoing and related objects, advantages and features of the invention should be more readily apparent to those skilled in the art, after review of the following Best Mode of Carrying Out the Invention, taken together with the drawings.